1. Field of the Invention
The present invention relates to a CMOS image sensor. More particularly, to a CMOS image sensor and method of fabricating a CMOS image sensor using a reduced number of processes.
2. Discussion of the Related Art
Image sensors are typically used for converting an optical image to an electric signal. The image sensors currently used in the art are generally categorized as either CMOS (complementary metal-oxide-silicon) image sensors or CCS (charge coupled device) image sensors. The CCD image sensor has superior photosensitivity and noise characteristics compared to the CMOS image sensor, but is difficult to incorporate in highly integrated systems has a comparatively high power consumption.
On the contrary, the CMOS image sensor uses simpler processes than the CCD image sensor, making it more suitable for the density of highly integrated systems. Additionally, the CMOS image sensor has comparatively low power consumption.
As the technology of manufacturing semiconductor devices has become more highly developed, many efforts have been made to research and develop the photosensitivity and noise characteristics of the CMOS image sensor.
Generally, each pixel of a CMOS image sensor consists of photodiodes capable of receiving light and CMOS devices capable of controlling the received light. Within the photodiodes, electron-hole pairs are generated which correspond to the wavelength and intensity of red, green and blue rays detected using a color filter. The out signals vary according to the quantity of the generated electrons, making it possible to capture an image.
A CMOS image sensor is shown in FIGS. 1A and 1B, and consists of a main pixel area 1 comprising a photocharge converting unit such as a photodiode 21, a dummy pixel area 2 provided outside the main pixel area 1, and a peripheral circuit area 3 for detecting signals detected by the pixel area 1 and the dummy pixel area 2. The peripheral circuit area 3 is formed so as to surround the main pixel area 1 and the dummy pixel area 2.
In the CMOS image sensor manufacturing process of the current art an oxide layer is coated on the surface of the sensor in order to form a device protecting layer 22 in order to protect a device from moisture or external physical shock. Additionally, a dark shield layer 23 is formed on the device protecting layer 22 corresponding to the photodiode 21 in order to shield the dummy pixel area 2 from light.
Subsequently, a planarization layer 24 is formed with its surface being planarized. Then, a microlens 25 is formed on the planarization layer 24.
Thus, in the manufacturing processes currently used in the art for forming the dummy pixel area 2 and main pixel area 1, the dummy pixel area 2 forming process requires an additional process in order to form the dark shield layer 23 to shield the area from light.